Granny Flat Plans and Prices in Australia: What You Need to Know

If you’re exploring granny flats plans and prices in Australia, you’re likely wondering what it really costs to build one. Depending on the size, design, and level of finishes, prices can start from as low as $30 per square metre, with full builds typically ranging between $20,000 and $200,000 or more.

A granny flat is a smart, affordable way to add value and space to your property. Whether you’re planning to house extended family, earn extra rental income, or create a self-contained guest space, building a granny flat offers a flexible alternative to major home renovations or extensions. With a wide variety of customisable granny flat designs and plans, it’s easy to find a solution that suits your budget, block size, and lifestyle.

In this comprehensive granny flat cost guide, we’ll cover:

• Key factors that influence granny flat pricing

• Average cost to build a granny flat in Australia

• Planning, approvals, and council fees

• How to compare quotes from granny flat builders, and more.

Want to find granny flat builders near me in Sydney, Melbourne, Brisbane, Perth or Adelaide?

How Much Does a Granny Flat Cost?

If you’re wondering how much to build a granny flat in Australia, the answer depends on the type, size, and level of finishes. The typical granny flat cost ranges from $80,000 to $200,000, although some basic options start much lower. Let’s break down granny flats plans and prices based on structure type and number of bedrooms.

Types of Granny Flats: Plans and Prices

The cost of a granny flat is largely influenced by the type of construction you choose. Here’s a quick granny flat price list to help you compare different options:

Attached Granny Flats

Attaching a granny flat to your existing home—such as converting a garage or underused space—is often the most affordable route. Prices can start from $10,000 to $20,000 for a basic conversion. However, a fully custom-built attached granny flat may cost just as much—or more—than a detached version.

Detached Granny Flats

Detached granny flats offer more privacy and flexibility, making them ideal for rental opportunities or independent living. Expect to pay between $25,000 and $45,000 for a basic build, with costs increasing for larger or more customised layouts.

Flat Pack Granny Flats

Flat pack options are budget-friendly and come with prefabricated components for on-site assembly. Prices typically range from $10,000 to $30,000, but you’ll need to account for additional costs such as site preparation, trades, and fittings.

Granny Flat Kits

Granny flat kits offer a slightly more complete package than flat packs. These usually include all materials needed to build a 45–60m² flat. Kit prices start around $20,000 to $50,000, with total project costs reaching $80,000 to $120,000 when professional builders are involved.

Prefabricated Granny Flats

Prefabricated (prefab) granny flats arrive on-site nearly complete and can be installed in just a few days. These dwellings typically cost between $50,000 and $80,000, offering speed and convenience without compromising on quality.

Custom-Built Granny Flats

If you want a fully tailored solution, a custom-built granny flat may be your best option. Prices vary widely depending on size, design, and finishes, ranging from $50,000 to over $200,000.

Granny Flat Cost Estimates

Save Money with Owner-Builder Options

If you’re handy and want to cut costs, building your own granny flat as an owner-builder can be a smart move. Just remember—each state in Australia has specific licensing, insurance, and permit requirements, so be sure to check the rules before getting started.

You might like: How much does it cost to build a house?

Custom-Built Granny Flats: How Much Does It Cost to Build?

If you’re considering a custom granny flat, prices will vary depending on the number of bedrooms, level of finishes, and the complexity of your design. Here’s a breakdown of granny flats plans and prices for custom builds by bedroom count:

1-Bedroom Granny Flat Cost

💰 Estimated cost: $80,000 to $130,000+

One-bedroom and studio granny flats are the most common due to their compact size and affordability. These layouts usually require 60 square metres or less, making them ideal for most suburban backyards. Custom designs allow for creative freedom—whether you want a simple open-plan layout or a more premium design with indoor-outdoor flow.

2-Bedroom Granny Flat Prices

💰 Estimated cost: $110,000 to $160,000+

Two-bedroom granny flats are perfect for accommodating families or long-term guests. These typically need 70–80 square metres of space and are often built close to the main house for easy access. On larger blocks, they can serve as rental accommodation with separate entry—ideal for couples, students, or elderly relatives. With a custom design, you can tailor the layout to include open-plan living, dual bathrooms, or alfresco areas.

3-Bedroom Granny Flat Cost

💰 Estimated cost: $185,000 to $220,000+

If you have ample backyard space, a three-bedroom granny flat offers the feel of a standalone home. It’s a great choice for extended families, larger households, or rental income. Custom-built 3-bedroom granny flats offer versatility, privacy, and long-term value—especially when designed with modern finishes and thoughtful layouts.

Want to find granny flat builders near me in Sydney, Melbourne, Brisbane, Perth or Adelaide?

Factors that affect granny flat build cost

How much does a granny flat cost to build? The total granny flat build cost depends on a range of variables that influence both the base price and the final figure. Whether you’re building a granny flat in your backyard or on a new site, here are 10 key factors that can impact granny flats plans and prices:

1. Size and Layout

The overall size and granny flat design play a significant role in determining the cost. Larger and more complex layouts and more bedrooms will generally be more expensive to build.

2. Type of granny flat

Whether you opt for a custom granny flat, prefabricated, or a conversion, this choice will be a major influence on the total cost of your build.

3. Materials

The choice of materials for construction can have a substantial impact on costs. Higher-quality and more expensive materials will increase the overall cost of the project.

4. Labour Costs

Labour cost, including skilled tradespeople and construction workers, can vary depending on the region, availability of workers, and the complexity of the project.

5. Location

The location of the property can affect granny flat build costs due to differences in local building codes, zoning regulations, and site conditions. Transportation costs for materials may also vary based on location.

6. Site Preparation

If the site requires extensive preparation, such as clearing, grading, or addressing drainage issues, it can add to the overall cost.

7. Permits and Approvals

Obtaining necessary permits and approvals from local authorities can involve fees and administrative costs. Compliance with building codes and regulations is essential and can affect the overall cost.

8. Utilities and Services

Connecting the granny flat to existing utilities, such as water, electricity, and sewer systems, can contribute to the overall cost. If these connections require significant work or upgrades, costs may rise.

9. Design and Features

The complexity of granny flat designs and the inclusion of additional features, such as high-end finishes, custom fixtures, or specialised construction techniques, can increase the overall cost.

10. Contractor’s Experience

The experience and reputation of your granny flat builder can seriously impact costs. More experienced contractors may charge higher fees, but their expertise can often mean a smoother and more efficient construction process.

It’s important to work closely with a qualified architect, builder, or construction professional to get accurate estimates based on the specific details of your project and local conditions when you’re building a granny flat in backyard.

You might like: How much does a house extension cost?

Other costs to consider when building a granny flat

When budgeting for your granny flat project, it’s important to factor in more than just the construction itself. Many additional costs can influence your overall granny flat build cost, and these can vary depending on your site, design, and chosen builder.

Here are some common extra expenses to budget for:

• Concrete slab
• Council and permit fees
• Utility connection (plumbing, electrical, sewerage)
• Retaining walls
• Landscaping
• Air conditioning/heating
• Hot water system
• Painting
• Tiling, flooring, decking
• Waste removal

When comparing quotes from granny flat companies, always ask for a full breakdown of what’s included and what isn’t. This helps you avoid unexpected costs and gives you a clearer picture of the total investment required.

You can also use a granny flat cost calculator online for a rough estimate based on your location, size, and chosen features—great for planning your budget more accurately.

You might like: How much is Lenders Mortgage Insurance?

Building requirements and granny flat approval cost

Planning permission regulations for building a granny flat differ across states. In New South Wales, recent legislation, the Affordable Rental Housing – State Environmental Planning Policy (SEPP), has been introduced to simplify the approval process for homeowners constructing granny flats. This policy allows residential property owners to bypass certain granny flat approvals, subject to meeting specific minimum requirements.

States or local council (TAS & QLD) set size limits for granny flats. For example, in NSW, the site must be a minimum of 450m2 with a 12m frontage, and the flat’s size cannot exceed 60m2. Compliance with building standards means you need to engage qualified builders, plumbers, and electricians, just like with a regular home construction.

Check with your local council for specific granny flat building rules and council fees for the approvals process.

Getting quotes for granny flat costs

Still wondering how much does a granny flat cost? Getting quotes from granny flat builders is easy with Yellow Pages. You can research and shortlist builders with our online directory and reviews before requesting and comparing multiple quotes.

Be sure to provide them with basic details about your project, including the size of the granny flat, any specific features you want, and your location. Many builders will conduct an on-site inspection to assess the specific conditions and requirements of your property. This allows them to provide a more accurate and tailored quote.

Request written quotes from each builder. This should include a detailed breakdown of costs, including materials, labour, permits, and any other relevant expenses. Ensure that the quotes are comprehensive and transparent before comparing them carefully. Consider not only the total cost but also the included services, timelines, and any warranties offered.

When choosing the right builder, be sure to:

• Check their references
• Clarify the T&Cs for payments schedules, work timelines, etcetera
• Check they are licensed and insured to work on your property
• Ask about included warranties

Remember that communication is key throughout this process. Clearly articulate your expectations, and don’t hesitate to ask questions. It’s essential to have a solid understanding of the project scope and costs before making a decision.

Want to find granny flat builders near me in Sydney, Melbourne, Brisbane, Perth or Adelaide?

*All costs and prices quoted were sourced at the time this cost guide was written and should only be used as an estimate.